I got the chance to put my car on a dyno last weekend and was surprised with the results. I have a 91n/a with a cone intake, RB header and RB catback. The car also has 16" wheels, and the a/c is not hooked up. Thats the jist of the mods and the results were 116.8hp/102.7 torque at 7.5 rpms. I was very surprised to see the results so low. The car car runs strong, I have never had any problems with it. When I first bought it the auxilory ports were stuck, but I fixed that problem ASAP. Can anyone help me and tell me why these numbers are so low. I have had only oneinsight on this, a friend said he thought my clutch was slipping. But I dont fell anything wrong with it, and it s just over a year old. I also dont ride the clutch either, but I bought it from NAPA. Any thoughts would be great.

Jason

 

One more thing, I had to replace the tranny, and it has a S4 tranny in it.

 

How many miles? What was the last compression test?, When was the last major tune-up? Do you have a previus dyno run to compare this against? What were the A/F ratio's?

 

doesn't sound too far off for a NA to me. Perhaps a little low, but not radically low.

 

There are 142k miles on the original engine. I have never had a compression test done on it. I actually called today on my way home for a price for a comp. test. 100 bucks, geesh. This was the first dyno I ever had done to it, so I cant really compare it to anything except my friends results. As for the A/F ratios, I dont know.

 

I pretty much have the same set up on my 88 GXL. RB Header,S.S Brullen Catback, Hi-flow cat, Crane Cams Ignition Box, RB Spark Plug Wires, K&N Filtercharger, Custom Cold Air Box, electric fan, non functioning 6 ports at the time(replaced with PR sleeves).

I only belched out 114.3 max hp,121 max torque. I thought he set the dyno settings wrong. I do find It strange that my Torque Is higher than my HP. Shouldn't It be the other way around?

 

those numbers do seem really low. I thought the n/a was supposed to have like 140-160 hp

 

Since those are RWHP numbers, they will account for any frictional losses in the drivetrain. Sometimes even making a pull in the wrong gear will skew the numbers. What gear did you pull in?

Assuming a 160HP (I know, probably not at 142K, but bear with me), add 10HP for mods, you get 170HP. Assuming frictional losses are usually between 20% and 30%, you can assume a relative HP number should fall between 119-136HP. So you aren't too far off. Possibly the state of tune of the could be off, you might want to give the ignition components a look over.

Do yourself a favor, if you plan to try this again. Collect all of the items you wish to test but don't install them. Map out a plan for which items will go on in what order to maximize your dyno time. You would be surprised how many pulls you can get in a 2 hour block if you organize it right. Make another initial pull to set your baseline, then proceed to install and test your individual components and note the results. Take good notes of ambient temp, engine coolant and oil temps, and weather factors. You want to make as many runs as possible in the same block so that outside factors like weather don't change and muck up the results.

Then come back here and brag to us how many HP you found!

 

Weel, for one, when the test was done, it was about 8 pm in the evening. But it was very humid that day and was still very warm at the time. So Im sure the weather played a part in it. But it doesnt subside the fact that my friends results were better in the same conditions.

Could a bad/slipping clutch be the same as Quote "frictional losses in the drivetrain."?

 

does sound low to me. Quick question: You said you have a header and catback. What are you running in the middle? Silencer or Cat?

What is the status of the little stuff like spark plugs?
If the clutch is slipping, that could account for some of the problem...but you also mentioned you dropped in an S4 tranny. Did you reuse the clutch?

 

There is no mystery to the low rwhp
Like I said in another post, about N/a fc's don't expect alot of power even with ton o' mods... I backed up what I said in the "mazdatrix thread" by drag racing my car on friday night and running almost exactly what I said I would run and the resultant horsepower, some people chose to hurl insults at me saying I did not know what I was talking about, however clearly I do, and the responses in this thread back up my assumptions and theories.. So how much Hp do you your cars would have without the mods? 50, 60, 70?.. Mine makes a 107 rwhp and runs 16.8/83 mph at 3800 ft, this is perfect tune with header/presilencer/catback cone intake, airpump actuated ports and throttle body mods on a S4 base with 120,000 miles on the original .. The compression is good and shows about 120 psi per rotor face, the sad fact is , is that n/a efi 13b's just dont make alot of power..The airflow meter and long runners don't help peak horsepower, but the general ideology of the efi 13b's was to have good driveability via more bottom end torque, and better combustion effiency to reduce emmisions. If you wanted real power, Mazda sold the turbo model for a reason, other than to just have a reason to print turbo stickers..
Now don't get all foamy at the mouth because I said they were gutless sloths out of the box..
I think if you were gonna chase n/a performance, you would have to resort to some extreme porting, possibly changing to a different manifold to match the breathing of a better housing port, abandon any form of muffling and go for a header/ straight pipe combo, lighten the hell out of the car and the rotating assembley, and be prepared to drive the car like a race car.. At this point though if you still want a decent fast street car with half assed decent driveability, a turbo would have been a better choice, when I say decent fast I mean 13.5-14.5 in the quarter, not 16+...Max

 

haha thats a pretty classic line. I dont know about attacking you or anything but I will challenge your statement. Im currently building up my NA and from how it performed when everything was running well I know it has potential. I also have an S4 and I'll dyno it once I have the mid pipe, headers and intake. THat should make us even mod wise.

 

Well the potential is there I agree, but without doing some drastic changes to the intake manifold and engine porting, as I said its not gonna be a real quick street car, it may be a fun, semi spirited car to rip around in, but if you pulled up against something like a camaro, or even a duster with healthy small block, you are gonna get your clock cleaned by it.. A quick street driven RX-7 needs about 215-250 at the wheels to be able to fend off most other factory pony cars, and with an n/a those kinda numbers are gonna be tough, you are a gonna have to havea ported engine, and really well ported engine.. Now with a turbo or good ole size n2o kit, you could do it with ease..
Glad you liked my 'line'....Max

 

Well, 15% drivetrain loss is with a new drivetrain and clutch. At around 150K miles expect that to change. When the tolerances start to loosen up, torque transmission losses increase significantly but I have a feeling in this case, the clutch would make a difference in numbers. How old is the clutch? I was also one of the doubters on the mazdatrix thread like maxthe7man. I think people wrongly assume that with each mod they do it is a cumulative effect meaning just because the exhaust was supposed to give you a 20% increase in power and your intake mod was supposed to give you a 5% increase, now they are making 25% more power. That only works for the Honda Rice boys. More often, as is the case here, the results are pretty conservative.

 

Jason,
It's TII time.

 

I would debate the "sloth" statement solely from what I have seen in Club Racing. Most front-running IT cars are making around 190-200 hp at the crank which shows up as 160-175 hp at the wheels. The only allowable mods to an IT internally are balance and blueprint and different apex seals. Hardly mind-boggling. Exhaust is free, and anything forward of the AFM is okay as long as it isn't ram air.

The first item I would suggest is the rear gear. Many people spend lots of money on mods, then leave the grocery-getter 3.90 or 4.10 in the rear. What do you want, acceleration or MPG? At the minimum I would suggest the 4.30 from the GTUs, or possible the 4.88 racing gear, although don't expect ANY measure of gas mileage w/ that one! (BTW, the 17"-18" wheel mods, while they may look cool, also serve to kill the overall drive ratio even further.) Most of the 'stangs you are seeing on the street have a different gear in them. It's one of the first mods they make, and it makes a huge difference.

The second item I see is weight. Many guys with less than desireable performance numbers also have huge speaker boxes, subs, or golf clubs in the hatch. What do ya think will happen? Lose the junk and save the weight, or simply continue to throw your money at the car w/ no appreciable gain in performance. Your choice. Remember when you were wheel shopping and you spent an extra $50 per wheel to save 2 pounds each? Well that speaker box in the back weighs 30 pounds and it's free! (See where I'm going here?)

 

Well fist off, Im not trying to get huge HP out of my car. These mods were done a while ago, basically carryovers from an 88 I had. There is a presilencer between the header and catback. The plugs are only probaby about 2 months old. The clutch was replaced a year ago last march. And the S4 tranny was put in a couple months after that. Hey it was free and I was desperate. for a car.LOL

The only other thing I can think of besides the clutch going is that there is a slight hesitation at 6200 rps. It only last about 800-1000 rpms though. Feels like I have a fuel problem. But at 7 grand or so, all the power comes back. You can even see that on the dyno.

As for the TII, I am curently saving the money form one. Even though I have seen 2 nice n/a's for sale.

 

any car that has a somewhat aged losses compression, the injectors dirty up, when things get used alot they dont work as good as they used to, thats why when people say this gives you 10 horsepower, each car is different whether it is a difference from humidities, altitude, so many aspects make your power different and you dont even know it. also tuning of these cars makes the biggest difference...

 

That hesitation is what i had when my n/a fc was running about 10-1 air fuel ratio! Next time you get it dyon'd, go to a dyno with a wideband. That will tell you exactly where your car is running right and wrong.

However, i do think it is a bit low. I put down 167rwhp with my FC. I should be putting down a couple more hp since i've done some more mods, and increased the air flow % by about 2-3. My advice is do some porting to the intake manfilold, and get a s-afc. Good luck, CJ

 

For cars that had 146 stock, they are never gonna see anywhere near that kind of power at the wheels with exhaust and intake, I own far to many Fc's and have spent to much time around these cars to buy that one...
However I do agree with your gear statements, althoug I find the first gear awefully short in the Rx's as it is.. More torque is what I would like to see first..
The wieght issue has been thrown around as well, my se is around 2820 with driver, I am trying to trade for an aluminium hood at this moment..Sub boxes are for kids...
My motor in my se runs pretty good, I was gonna go for a heavily ported n/a motor next, but the S4 and S5 TII motor/trans combos with a microtech is awefully cheap out of Australia, I found a deal that has all the stuff, stand alone ems, intercooler everything for 1800 aus$$.. its hard to justify na power when that kinda of deal is around, a few mods to that thing and it will be 2 seconds quicker in the quarter right off the bat..Max

 

This is something else that has me surious. I thought I posted it in the original post, but didnt. My friend dynod his right after mine. He has a S4, with the same mods as myself except he has a S5 tranny, and still has stock manifold to DP to Presilencer with HKS catback. His car has approx. 8k miles less than mine and he came up with 138hp. That is why I thought mine was to low to begin with. Any ideas?

 

I'd start looking at the 6 ports and vdi system. Wire them open/high, and take it for a spin. See if the butt dyno reads any higher. CJ